Technical Abstract:
Introduction
Total parenteral nutrition (TPN) in preterm human infants has been associated with increased incidence of sepsis and it has been suggested that sepsis may occur due to translocation of gut luminal bacteria (1). In the present study, we sought to identify the composition of microbiota in the neonatal pig gut, their relationship to translocation events, and to examine the effects of TPN versus enteral (ENT) feeding on early gut colonization.
Materials and Methods
Newborn, colostrums-deprived pigs (<24 h old) were fitted with intravenous catheters inserted into the jugular vein and divided into two groups. One group (n = 13) daily received only intravenous feeding (TPN). The second group (n = 13) was enterally fed an antibiotic-free, commercial pig milk replacer (ENT); the nutrient intake did not differ between groups. After 7 d of treatment, pigs were euthanized and tissues collected. Cultivation and differentiation of intestinal bacteria has been described (1). Suspected C. perfringens and C. difficile isolates were confirmed by colony morphology, the ethanol spore test, API Test Strips (bioMerieux), and by an enzyme immunoassay (2).
Results
Table 1. Colonization of segments of the intestinal tract by bacteria in ENT vs. TPN treated neonatal pigs
Pigs colonized (number of bacterial genera)
Treatment Jejunum <p>Ileum Cecum
ENT (n = 13) 11 (6) 13 (7) 13 (7)
TPN (n = 13) 2 (1)* 5 (3)** 13 (4)
Ent = enterally fed; TPN = total parenteral nutrition
*P = 0.0012; **P = 0.0016 by Fisher’s Exact Test
Bacterial translocation from the intestinal tract to tissues or blood was not different on the basis of treatment--each treatment group had 8 of 13 pigs with translocation events (data not shown). Bacterial concentration, number of bacterial species isolated, and the number of intestinal segments colonized were greater in the ENT group when compared to the TPN-treated pigs (Table 1). Bacterial concentrations, number of bacterial species, and frequency of isolation progressively increased from the J to the C. On the average, the ENT group had 2 to 3 log10 higher cfu/g of Enterococcus in the GI tract (particularly in the J and I) than the TPN group. The ENT group had 4/13 positive for C. perfringens and 1/13 positive for C. difficile toxin A production (Table 2). The TPN pigs had 0/13 positive for C. perfringens and 5/13 isolates positive for C. difficile toxin A.
Table 2. Isolation of Clostridium spp. from the gut of ENT vs. TPN piglets
<p>Site of Isolation Pigs pos. C.difficile
Treatment J**a I C (site)
ENT = 13 0 6 13 13 1 (C)
TPN = 13 5 4 9 11 5 (J, I, C)* **aJ = jejunum, I = ilium, C = cecum
*Different (P < 0.1) by Fisher’s Exact Test
Discussion
In our study, the authors hypothesize that C. difficile was able to colonize TPN pigs due to the reduced presence of commensals in the gastrointestinal tract of TPN pigs. Similarly, when the autochthonous microflora is absent, increased C. perfringens and C. difficile have been observed with cases of necrotizing enterocolitis of preterm infants (3).
We concluded that TPN was not positively associated with translocation, that ENT favored increased bacterial concentrations comprised of a more diverse speciation in the gastrointestinal tract, that Enterococcus is an early colonizer of the GI tract, that TPN retarded the colonization of the intestinal tract, and that TPN-treated neonates were at a higher risk of colonization by toxin-expressing strains of C. difficile.